The per-unit costs will be lower. The value of redeveloped land only goes up when its bought out to build density. If you currently live a mile out of the urban core in some sprawl mcmansion your house is probably worth 5 million right now in a lot of cities. If the city proper dropped zoning requirements and let density happen the price of your house will vary between the "loss in desirability" from being closer to an expanding urban core and the potential value of redeveloping your house. Your lot could end up being worth an order of magnitude more if the demand is there to put a high rise on it.
Some will win huge as major contractors want to replace your quarter acre sprawl development or row house with 10+ story urban and are offering absurd amounts of money for all the lots. Some will lose if nobody has the capital to redevelop their area and density goes up around it. But if you get the ball rolling there is so much pent up demand for urban migration and sustainable living that we could probably go decades of continuous development in most cities without the money drying up. Its an untapped gold mine of economic growth.
Some will win huge as major contractors want to replace your quarter acre sprawl development or row house with 10+ story urban and are offering absurd amounts of money for all the lots. Some will lose if nobody has the capital to redevelop their area and density goes up around it. But if you get the ball rolling there is so much pent up demand for urban migration and sustainable living that we could probably go decades of continuous development in most cities without the money drying up. Its an untapped gold mine of economic growth.